Accommodation of Hounsfield unit achieved from ct scans with grades of gray scale in CBCT images

Abstract

Background and aims: Cone beam computed tomography (CBCT) is an imaging system which has many advantages to Computed tomography (CT). In CT scan Hounsfield unit (HU) is proportional to the degree of x-ray attenuation by the tissue. In CBCT, the degree of x-ray attenuation is shown by gray value (Voxel value).The aim of the present study was to investigate the relationship between gray value in cone beam CT (CBCT) and Hounsfield units (HU) in CT scan. Method and Material: In this descriptive study, the head of a sheep was scanned with 3 CBCT and 1 medical CT scanner. Gray values and HUs are detected in images. Reconstructed data were analyzed to investigate relationship between CBCT gray values and HU. Result: A strong correlation between gray values of CBCT and HU of CT scan was determined. Conclusions: Considering the fact that gray value in CBCT is as the criteria in measurement of bone density before implant treatments, itI?s use recommended because of the lower dose and cost compared to CT scan.e Key Words: Hounsfield unit, Gray value, Cone beam Computed Tomography (CBCT), Computed Tomography (CT)